It is now recognized that innate immunity constitutes a formidable and essential component of the overall immune defense of higher vertebrates. One of the central pillars of innate immunity is the Toll-like receptors (TLRs). TLRs transduce the signals sparked by external stimuli through adaptor proteins characterized by the presence of Toll/interleukin-1 homologous region (TIR) domains. Four adaptors have been characterized, and a fifth, whose function is still unknown, has been identified. We have recently cloned a full-length zebrafish gene that bears sequence similarity to one of those characterized adaptor proteins, TRIP (or TICAM-1). TRIP has been shown to play an important role in antiviral immunity, relaying signals from TLRS to the nucleus, where transcription of immune-responsive genes is triggered. However, this putative zebrafish TRIP possesses at least two important structural differences that may alter its role in immune defense and may in fact be an altogether novel TIR-domain-containing adaptor protein. In this proposal, we intend to fulfill the following SPECIFIC AIMS: 1. Determine the role of the putative zebrafish TRIP in mounting an immune defense against both viral and bacterial pathogens 2. Determine how differences in residues at domains and motifs important to mammalian TRIP function affect signal transduction in zebrafish 3. Identify additional proteins that interact with the putative zebrafish TRIP A fuller appreciation of the components that comprise a comprehensive innate immune response will lead to a greater understanding of how vertebrates defeat invading pathogens. Armed with this understanding, the potential for effective disease prevention and intervention can be exploited, and important therapeutics can be designed and implemented. [unreadable] [unreadable] [unreadable]